Magnetically-driven crustquakes in neutron stars

Abstract

Crustquake events may be connected with both rapid spin-up `glitches' within the regular slowdown of neutron stars, and high-energy magnetar flares. We argue that magnetic field decay builds up stresses in a neutron star's crust, as the elastic shear force resists the Lorentz force's desire to rearrange the global magnetic-field equilibrium. We derive a criterion for crust-breaking induced by a changing magnetic-field configuration, and use this to investigate strain patterns in a neutron star's crust for a variety of different magnetic-field models. Universally, we find that the crust is most liable to break if the magnetic field has a strong toroidal component, in which case the epicentre of the crustquake is around the equator. We calculate the energy released in a crustquake as a function of the fracture depth, finding that it is independent of field strength. Crust-breaking is, however, associated with a characteristic local field strength of $2.4\times 10^{14}$ G for a breaking strain of $0.001$, or $2.4\times 10^{15}$ G at a breaking strain of $0.1$. We find that even the most luminous magnetar giant flare could have been powered by crustal energy release alone.

13 pages, 8 figures. Minor changes to match MNRAS-accepted version

References in corpus (8)

• The Breaking Strain of Neutron Star Crust and Gravitational Waves
• Corona of Magnetars
• Untwisting magnetospheres of neutron stars
• Magnetar-like Emission from the Young Pulsar in Kes 75
• Thermoplastic waves in magnetars
• Heating and cooling of magnetars with accreted envelopes
• The unusual glitch recoveries of the high magnetic field pulsar J1119$-$6127
• Molecular Dynamics Simulation of Shear Moduli for Coulomb Crystals

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• Magnetic-field evolution in a plastically-failing neutron-star crust
• Magnetar-like X-ray Bursts from a Rotation Powered Pulsar, PSR J1119-6127
• Spectrum of shear modes in the neutron-star crust: Estimating the nuclear-physics uncertainties
• Peculiar Glitch of PSR J1119-6127 and Extension of the Vortex Creep Model
• Magneto-Rayleigh-Taylor instability in an elastic finite-width medium overlying an ideal fluid
• Minimum Glitch of the Crab Pulsar and the Crustquake as a Trigger Mechanism
• Breakdown of the Goldreich-Julian Relation in a Neutron Star
• Burst and Outburst Characteristics of Magnetar 4U 0142+61
• FRB 121102: a star quake-induced repeater?